Tecnicas mineras para quarries

5 Natural Resource Management

17* Internationa Mining Congress and Exhibition of Turkey- IMCET2001, © 2001, ISBN 975-395-417-4

Technological and Economic Evolution of Diamond Wire Use in Granite or Similar Stone Quarries
R.Mancinİ, M.Cardu & M.Fomaro
Dipartimento di Georisorse e Territorio - Politecmco di Torino, Italy & CNR FIRGET, Torino, Italy

E.Lovera
Dipartimento di Georisorsee Territorio - Politecnico di Torino, Italy

ABSTRACT: Cutting with diamond wire saws in hard stones, such as granites, gneisses, syenites and diorites, taken together with the dynamic splittmg system, using a detonating cord, has become more widespread because of the operating versatility of the cutting machinery and because of the good productive results. It is obvious that there is anadvantage in marketing blocks which have finished-off faces, with no wastes in the squaring phase, especially when high-value dimensional stones are concerned. The excavation of channels within the good rock and the realization of artificial "easy ways" (splitting surfaces) could economically justify the higher cost of diamond wire technology in comparison with explosive splitting. The present paper,according to recent surveys carried out in many stone quarries in Piedmont and Sardinia, supplies new data in order to make a technical-economic comparison between different quarrying systems. about 1.5 Mt/y of other stones) is mainly the result of three well-established technologies: diamond wire sawing, chain cutting (for soft rocks only) and detonating cord splitting. In hard (granites andsimilar) dimension stone exploitation, the most economical production system, at least for primary cuts, is still splitting by explosives, which can be considered an extreme application of controlled blasting concepts and precision drilling techniques. Very thin linear charges, represented by strands of detonating cord, are placed in parallel, closely spaced holes, stemmed with a suitable shock-absorbingmaterial like water, and simultaneously detonated by a master cord. Fracture is due to tensile stresses in the rock interhole bridges, and excess energy from the blast provides the required small displacement of the separated mass (Mancini et al., 1996a). In wellconducted operations, the half casts of the holes are perfectly observed and no extra cracks occur. Productivity is high and İs dictatedby the drilling system (Mancini et al., 1994). Although there have been numerous research studies carried out by a lot of laboratories in order to improve the directional splitting action of explosive charges, the most commonly used technique İs still the conventional, firmly established detonating cord splitting method (an estimated 12000 km of cord is consumed yearly for this application inItaly). Examples of the application of this method are given İn Figure 1.
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1 INTRODUCTION The wide and heterogeneous family of dimension stones has in common the fact that they must be obtained in the form of commercial blocks, which means sound blocks of parallelepiped shape usually weighing 5 to 15 t, suitable for further processing and for the production of slabs or other architecturalitems. The mining stage of the dimension stone industry conforms to one of the two general strategies quoted below: A. large volumes of rock, usually in the range of thousands of m3, are removed by primary cuts from the rock body and, subsequently, stepwise, divided into commercial blocks; unsuitable material is discarded at this stage; B. commercial blocks are directly cut from the rock body; thismethod is mostly applied to very regular and homogeneous deposits and especially to underground operations. Ample cut or split surfaces have to be produced at a reasonable cost and without impairment of the rock soundness. 2 TECHNIQUES EMPLOYED IN ITALIAN QUARRIES Italian production of commercial blocks (nearly 5 Mt/y of marbles, more than 1 Mt/y of granites and

discarding (up to 5 times,...